Cleaning of cereal grains



Patented Sept. 14, 1943y g CLEAnINGoF CEREA'L GRAINS Y Y Leland H.LoguarDenver, Colo., assignor'toMin-fv, A' f 1 t f A ing Process andPatent Company, Ilenvcxz,

Colon a corporation of Delaware t Appliatin raeiiruairy 41o,1941,:seria1No; 373,313 reclama ,-(ciao3- 951)M This invention relatesto the cleaningand beneciation ofv grains and the likel and isillustrated herein asfapplied tothe treatment of cereal grains for theremoval of chaff, dirt, smut, insect eggs, insects andthe like fromgrain vprior to milling. c

The process` also may be applied tothetreatment offcereal grainspriorto'nilling for the removal of the hull or outer skin,y which, jinreality, is the true bran and hasflittle, if any, food value. n

A 'further application of the present invention to the treatment ofgrains is a selective sepafra` tionA of the vgrains vor kernels intovfrac'tion's,one offwhich would be most suitable forseed "pur-A poses,Whileanother fraction wouldbeseparatei vide'ka simple, inexpensive LandVex'pe`clitioi`1sfprovcess for removing' contaminating f matterffror'ncereal grains'. .Y Another object of the inventionisftof rovide Aio amethod for increasing' the food valueper-un'it of Weight of cerealgrainsby removingiltlfiere'iroin the outer hull value.

or bran 4contient' of negligible food A further .object of' theinvention is to provide a treatment for vgrading cerealgrains'laccording to variations in the protein content thereof.` ,K

Other objects reside in novel stepsY and treat-l ments, all of whichwill appear more fully in Vthe course of the following descriptionjAccording to the present invention', thenfriei clusive of the brancontent, ywill differ fromfth'e' grain kernels'in siz'e, shape andspecific'v gravity so that itis possible-to lget'ja sufcientlyjcleanseparation to satisfyordina-ry r"eq*uireinfantsl hydraulicclassification.4 As ya consequence;A the materials taken for treatrne"nt`y may @be condi-4 tioned for the Aseparation :according 'to difieren;tial wetting properties, but it yisfalso possibleto render thematerialbetter suited for"certai"l arations by the use of suitable dispersingrel -ents' and a, variety of separating methods may ployed inconjunction therewith.

A typicall separation involvingl the treatment of cereal grainsprimarily for the removal ofbran, but also veffective for removal ofdirtandhother contaminating matter'will now be describedin "Ihe graindelivered to an elevator or the like is iirs't fed in dry condition toay screening oper; ationvfor* the removal of coarse foreign matter, suchas Wood chips", wire, bolts andrthelike.

'The Yscreened product of"'this operation is` collectedfand'f'ed yto 'arevolving cylinder or the like,

such asaylarge ytrunniony ball mill, which'allows f only a low'pulpleveltc be carried. In"this`mi ll, the grain is mixed with sufficientVwater to make a lsemi-fluid massand where reagents are to be used -intheftreatment, they preferably are vin-j troducedinto themill to-attain'thefdesired de-f4 f gree of mixing; f y Reagents wellysuited` toacty as dispersants in the prsent treatmentfare sodaash and sodium'Lsilicate,y although othery reagents' possessing similarl propertiesvwhich ywill not vhave a .deleterious effecten the grain mayv be "used inplace thereof; The amount of reagent required in the treatment will"vary, according tothe nature ofthe subsequent treatment andthecondition ofthe-ma'- terial, but' from'one-tenth pound to' ive pounds ofreagent` per ton of grain will give satisfactory results.y y'

Either'the wetting medium, usually water, o1' the reagent of thetreatment tend to loosen and k.remove the outer skin from thegrain'kernel and the combined presence ofr these'agents' inthe millserves to soak the individual kernels and'loo'sens theouter'skin,'causing it to become detached from the kernels; Y f l Thetumbling,r action and the continual movement of kernels against one`another also assists in loosening' and separating this outer skin. The

ficient to insurev loosening andvfreeing the major percentage ofthefbran coverings fromithe `kernels, initial testing is' desirable todetermineth'e treatment time. From two tothre'e minutes will serve,y asa Vlower limit,l while up to ftwentyftovtwenty-tive minutes lconstitutesthe uppery vlimit of the treatmenttime. v 1

"After `treatmentinfthefmill, the discharging mass is diluted and passedtothe subsequent sep-L aratiori stage of ithefoperation." TheeXtent oidilution *may be varied and [usually ythree to' four parts water to onepart grain will insure good results,

In this example, the treatment at the separation stage consists.inieeding the dilute mass The bran particles, together Withthecontaminating matter, are maintained in a dispersed` conv dition underthe action `of the reagent and kept from forming iiocs which might tendto sinkdue to their dispersed condition, remain at the surface and passacross the tailings discharge.

Other types of hydraulic classification may be employed in place oftable concentration. Jigs and' hindered settling classiers are cited asother types of equipment which may be used.

Another use of the present invention is to grade the constituents of acereal grain according` to variations in its protein content. In such anoperation, the grain which preferably is a precleaned product, isintroduced into the tumble mill in the presence of the wetting mediumand 1 `subjected to a conditioning operation of not to and also are keptfrom depositing on thegrain surfaces with which they come in contact, as

might otherwise occur if they `were not respond. Y

ing to the action of the reagent. V

As a consequence, this matter because of its lighter specific gravityforms` an overlying stratum and remains in a state of semi-suspena sionin the Water `or wetting medium flowing across the deck of the tableandis carried thereby over what is normally considered the tailing side.`As a` resultk of this series o f treatments, the grain discharged atthe. concentrates end of the table is in a substantially clean conditionand free from any appreciable quantity of its koriginal bran content.`The b ran removal also servesto effectively separatel contaminants ofmineral, vegetable `and animalroriginf, anda,s a consequence., thenalgrain concentrate isa substantially pure product possessing highfoodvalue. y

` vWhile the treatment hereinbeiore described is Well suited for thetreatment of what may be broadlyclassifled as cereal grains', ithasyparticular application to the treatment of wheahbarley,- rye, corn andoats. f

The wetting;A medium of the treatment preferably consists of-water, but`may be any other liquid or solution possessing the desiredwettingqualities which will not lhavea contaminating or injurious effect on thegrains. g Y

In another treatment, it was desired to retain thevbran i-n the grainand merely subject the grain to a cleaning operation for the removal ofcontaminants. v Y l As an extended period of conditioning ith thereagent will loosen the skin, it its necessary in such an operation tohold the rconditioning time to a minimum, as well 'as to avoid a pro--Unounced'attrition action. Therefore, the mass subjectedk to theagitation in the tumblingl `action is passed through the treatment infrom two to three minutes, Which serves to provide the de.-

sired differential wetting action.

In thisl connection, it will be understood that the liquid content inthe conditioning operation may be increased, and thereafter lessadditional dilution will be necessary to properly prepare the materialfor the hydraulic classification.

Furthermore, While it is preferable to initially condition the materialin a tumble mill, any other form of=mixing which will serve to bring thereagent into contact with the solids content to be removed by theclassification may be substituted therefor. Fory example, a conditioningtank provided with rotary ragitators may be used. f

yAfter the conditioning treatment, the product is diluted as requiredand subjected to the final separation by feeding it to a concentratingtable Where the grain tending tosink because of its wetted conditionpasses across the concentrates discharge While Chau. insects.. dirt andthe like.

` different wetting characteristics which' permit Y sink or might becomeentrapped withfthe rof the aforesaid operations.

exceed four minutes. The grain of high protein content which; has thebest food value wets rst, while the low protein content which has thebest seed value wets last. The discharge of the conditioning treatmentis diluted sufiiciently to form a free-flowing pulp and subjected tostratifying classification.

Due` to the diiierences in the wetting properties. the high proteincontent -will sink and be held in the riiiies` to pass to theconcentrates discharge, while the lowv protein content forms anvoverlying stratum which moves across the rimes to the tailings dischargewhere it may be collected as a second valuableconstituent of theoperation.

It will be understood that all the.` foregoing treatments will notdepend upon the use ot a reagent, as the materials to be separatedpossess a satisfactory recovery by the use of hydraulic classification.However, the use of a dispersing agent serves to keep certain fractionsof the contaminant matter from depositing on grain surfaces and fromgathering in docs which might temi` to content.

The accompanying flow sheet represents an operation well suited toattain the objects of any In thistroatment grain after an initialscreening operation t@ removeoversize foreign matter, passes into a comditioning stage to obtain the differential wet. ting and, if continuedfor a suiiicient interval, to remove the outer. skins from the grainkernels.

Following this conditioning operation,r the grain is subjected tohindered settling in an air-free liquid.` The grain, or grain of highprotein content, sinks in the liquid, while chaff, foreign matter andother contaminants pass to the surface and are removed.

f The cleaned grain is then subjected to the l action of a centrifugeand passed to a drier from which it is discharged as a dried and cleanedfinal product. f y

Air-.free liquid. as used in thefdescription and claims is intended todesignate a liquid con taining no gas other than the normal amount ofoxygen present by reason of sui-faceabsorp tion'. It is also possible touse the same treatment operations in conjunction with an agglomeratingseparation by the use of suitable agglomeratq ing agents. Features ofthe agglomerating action described but not claimed herein have beenLmade y `the subjects matter of claims in my co-.pending application ofeven date, Serial No. 378,317, en-

titled Agglomeration of cereal grains. y n

kChanges and modifications may be availed of within the spirit and scopeof the invention as defined in the hereunto appended claims.

What I claim and desire to secure by Letters Patent is: f .i

graim l. In a process of separating grain kernels from the outer skinsof their natural formation, the steps of treating cerealgrain in anaqueous carrier vehicle, and during said treatment agitating the grainsubmerged in Isaid vehicle for an interval sufficient to loosen theouter skins and differentially Wet the grain kernels and said skinswithout substantially reducing the grain kernels, subjecting said skinsupon loosening to the influence of a dispersing reagent, causing saidloosened skins While subject to the dispersing influences of the reagentto collect in suspension at or near the surface of the liquid inoverlying relation to said grain kernels by subjecting the submergedsolids to a vibrating table treatment capable of exerting a suspendinginfluence on said skins,A and recovering the solids so separated atseparate points of discharge from the treatment.

2. In a process of separating grain kernels from the outer skins oftheir natural formation, the steps of treatingcereal grain in an aqueouscarrier vehicle, and during said treatment agitating the grain submergedin said vehicle for an interval suilicient to loosen the outer skins anddifferentially wet the grain kernels and said skins withoutsubstantially reducing the grain kernels, subjecting said skins uponloosening to the influence of a dispersing reagent, causing saidloosened skins while subject to the dispersing influences of the reagentto collect in suspension at or ynear the surface of the liquid in soverlying relation to said grain kernels by subjecting the submergedsolids to a ligging treatment capable of exerting a, suspendinginfluence to attrition in a tumbling action for an interval sufficientto loosen theouter skins and differentially wet the grain kernels andsaid skins, subjecting said skins after loosening to the iniiuence of adispersing reagent, then causing said loosened skins While subject tothe dispersing influences of the reagent to collect in suspension at ornear the surface of the liquid in overlying relation to said grainkernels by subjecting the submerged solids to a classification treatmentcapable of yexerting a suspending influence on said skins, andrecovering the solids so separated at separate points of discharge fromthe treatment.

4. In a process of separating grain kernels from the outer skins oftheir natural formation, the steps of treating cereal grainy in anaqueous carrier Vehicle, and during 'said treatment maintaining thegrain submerged in said vehicle, initially subjecting the immersedygrain to attrition in a tumbling action for an interval sufficient toLloosen the outer'skins and differentially Wet the grain kernels and saidskins, diluting the product of the attrition action, subjecting saidskins after loosening to the inuence of a dispersing reagent, thencausing said loosened skins while subject to the dispersing innuences ofthe reagent to collect in suspension at 0r near the surface of theliquid in overlying relation to said grain kernels by subjecting thesubmerged solids to a classiiication treatment capable of exerting asuspending influencel on said skins, and recovering the solids soseparated at separate points of discharge from the treatment.

5. In a process of separating grain kernels from the outer skins oftheir natural formation, the steps of treating cereal grain in anaqueous. carrier vehicle, and during said treatment maintaining thegrain submerged in'said vehicle, initially mixing the cereal grain withay suflicient quantity of the carrier vehicle to make a semiiiuid mass,subjecting the semi-iiuid mass to attrition in a tumbling action for aninterval sufncient to loos/en the outer skins and diierentially Wet thegrain kernels and said skins, dilutingy the product of the attritionaction, subjecting said skins after loosening t0 the influence of adispersing reagent, then causing said loosened skins while subject tothe dispersing influences of the reagent to collect in suspension at ornear the surface of the liquid in overlying relation to said grainkernels by subjecting the submerged solids to a classification treatmentcapable of exerting la suspending influence on said skins, andrecovering the solids so separated at separate points of discharge fromthe treatment.

6. A treatment according to claim 5 in which the semi-fluid mass issubjected to attrition for an interval of from two to twenty-fiveminutes.

LELAND H. LOGUE.

